Are ocean asteroid impacts really a serious threat?

If a space rock were to hit the Earth at just the right location in the oceans, it could cause massive waves that could inundate U.S. coastlines, a new computer simulation suggests.

For instance, if an asteroid were to hit the continental shelf off the Maryland coast, it could produce 23-foot-high waves, causing flooding from New York to Georgia that would take hours to recede. A similar impact off the coast of California could flood major power plants along the coast, the rese...